Plunger stopped bi-directional no-back assembly

ABSTRACT

Apparatus comprising a rotatable output member, a rotatable drive member for rotating the output member in either direction, a releasable brake for substantially preventing rotation of the output member in either direction when it is not being driven by the drive member, and apparatus on the drive member is operable to release the brake upon a predetermined rotation of the drive member in either direction.

United States Patent 1151 3,695,402 Klemm 51 Oct. 3, 1972 [54] PLUNGERSTOPPED BI-DIRECTIONAL 2,626,027 l/ 1953 Anderson ..192/8 NO-BACKASSEMBLY 3,449,978 6/1969 Stimpson ..192/8 721 t:Ed'O.Kl S ,M'h. 1 i orr agmaw Primary ExaminerBen amm W. Wyche Asslgneei gm ProductsCorporation Assistant ExaminerRanda1l Heald Saginaw, Mlch-Attorney-Learman 8!. McCulloch [22] Filed: June 11, 1970 ABSTRACT [21]Appl. No.: 45,291

Apparatus comprising a rotatable output member, a rotatable drive memberfor rotating the output [52] US. Cl. ..l92/8 R member in eitherdirection a releasable brake for [51] Int. Cl ..Fl6d 67/00 stamianypreventing rotation of the output member in Fleld of Search e th d c o eit i not being driven e drive member, and apparatus on the drive memberis [56] References and operable to release the brake upon apredetermined UNITED STATES PATENTS rotation of the drive member ineither direction.

1,074,175 9/ 1913 Howe 192/8 17 Claims, 7 Drawing Figures PAIENTEUuc'r a1912 I I 3' 1 35 FIG. I 7

INVENTOR H 6 .EO V- 0. ALEMM BY AM ATTORNEYS PLUNGER STOPPEDIll-DIRECTIONAL NO-BACK ASSEMBLY This invention relates to no-backapparatus, and more particularly, bi-directional no-back apparatus forsubstantially preventing the rotation of an output member when it is notbeing driven in either direction by the input member.

There are many instances in which the exact positioning of a loadcarrying member to be moved is critical. Many of the devices which mustbe so positioned include a rotatable output member driven by a rotatableinput member. In some applications, after the driving force applied tothe rotatable input member has been removed, the force exerted on theoutput member by the load carried thereby is such as to rotate theoutput member in a direction opposite to that in which it was driven bythe input member. In other instances, when the output member is beingdriven, the load is applied in a way such as to cause the output memberto be driven at a rate faster than the rate at which it was being drivenby the drive member. In this latter situation, the output member isactually no longer being driven by the input member although the drivehas not been disconnected, and the runaway condition which resultsfrequently causes an improperly positioned load, and may also behazardous. In either instance, it is imperative that the output memberbe substantially prevented from rotating when driving force is no longerbeing exerted, to accurately position the output member and the loadconnected thereto.

Accordingly, it is an object of the present invention to provideapparatus for substantially preventing rotation of a rotatable outputmember in either direction after the force driving the input member hasbeen removed therefrom.

When relatively small loads are to be moved with the rotatable outputmember, the torque exerted by the load tending to move the output memberin either direction is relatively small. Accordingly, it is anotherobject of the present invention to provide inexpensive, reliablebi-directional no-back apparatus which is particularly suited forrestraining relatively small loads.

Braking and clutching assemblies incorporating friction discs have beenutilized in prior art no-back devices, however, disc wear in theseassemblies is generally a limiting factor in achieving a highly reliableproduct. To insure operability, the position of the friction discsrelative to each other must bevcontinuously adjusted, thus limiting theflexibility of operation. Accordingly, it is a further object of thepresent invention to provide bi-directional no-back apparatus which willoperate substantially independently of friction disc wear.

If the no-back mechanism is constructed of parts which move into wedgedrelation to effect the braking force, a high starting torque must beexerted to release the no-back mechanism. Accordingly, it is stillanother object of the present invention to provide bidirectional,no-back mechanism, for positively braking an output member, which doesnot require a high starting torque for release.

A jack screw, commonly employing a screw shaft cooperating with arecirculating ball nut to raise a load supported on the nut, is atypical application with which the bi-directional no-back apparatus,formed according to the invention, may be utilized. Because of the highenergy transmitting efficiency of the recirculating ball nut and screw,when the load has been raised to the proper level, and the load liftingforce on the screw is removed, the downward force of the load exerted onthe nut will tend to rotate the screw in a reverse direction so as tolower the load from its proper position. Accordingly, it is yet anotherobject of the present invention to provide no-back apparatusparticularly suited to this situation for preventing the reverserotation of a load positioning member while permitting the member to befreely driven forwardly.

When a load supported on a jack screw of this type is to be lowered, itis important that the lowering be accomplished quickly, easily, andwithout the manipulation of unlocking levers, or the like, which must bereset to release the no-back apparatus prior to the screw shaft beingdriven in an opposite direction.

Accordingly, a still further object of the present invention is toprovide bi-directional no-back apparatus which will eliminate thepreparation necessary in some prior art devices to move the outputmember in either direction.

Briefly, according to the present invention, there is provided an inputdrive member, means journaling the input drive member for rotation,means for revolving the input drive member in either direction, anoutput member to be driven, means joumaling the output member forrotation in either direction, means coupling the input member with theoutput member, releasable brake means for selectively substantiallypreventing rotation of the output member in either direction when it isnot being driven by the input drive member, and releasing meanscooperating with the drive member and operable to release the brakemeans upon rotation of the output member in either direction by thedrive member.

In the drawings:

FIG. 1 is a side elevational, sectional view of bidirectional driveapparatus for controlling the rotation of a screw shaft which isconnected with a recirculating ball nut;

FIG. 2 is a side elevational view illustrating only a sleeve which ismounted on the screw shaft;

FIG. 3 is an end elevational view of the sleeve, taken along the line 33 of FIG. 2;

FIG. 4 is a fragmentary end elevational view of the input drive memberonly illustrating particularly the brake releasing portion thereof;

FIG. 5 is an end elevational view of a braking disc which is mounted onthe screw shaft for braking the rotation thereof;

FIG. 6 is a transverse sectional view taken along the line 6 6 of FIG.1; and

FIG. 7 is a fragmentary, end elevational view, similar to FIG. 6, andillustrating the input drive member in a slightly revolved position.

Referring now more particularly to the drawing wherein a preferredembodiment of the invention only is illustrated, an outer housing H forthe no-back mechanism is shown as including an annular tubular section8, formed with an internal annular boss or rib 8a, and telescopinglyreceiving an annular tubular section 9 having one end butted against theboss 8a. The tubular section 8 mounts, at one end, a ball bearingassembly B, joumaling a rotatable, generally cylindrically shaped inputdrive sleeve member D. One end portion 12 of the drive member D isprovided with a keyway 12a to receive a key which may secure a rotatabledrive pulley (not shown), or the like on the member D. At its oppositeend, the drive member D is provided with an annular flange 16 having anundulating peripheral edge which includes a plurality of lobes andcurvilinear recessed portions 16a and 16b, respectively. The bore 14through the sleeve D communicates with a pair of diametrically opposedslots 18 (FIG. 4) having radially diverging marginal walls 18b and 180.

A typical use for the no-back apparatus is with a screw shaft S whichmay extend through the driver sleeve D and has a threaded portion 22cooperating with a recirculating ball nut 24, which includes a pluralityof recirculating balls 24a received within the threads, in the usualmanner. A load receiving member such as a jack, schematically shown atL, may be connected with the recirculating ball nut 24 for movementaxially in a linear path when the screw shaft S is rotated.

An annular sleeve 26 is mounted on the nonthreaded screw shaft portion20 and includes an annular flange portion 32 of slightly increaseddiameter secured to the shaft portion 20 with a pin 27. The sleeve 26 issupported for rotation within the tubular section 9 by an annularbearing assembly 29 which is axially fixed by snap rings 30 and 31provided on the hub 26 and housing section 9, respectively. Integrallyformed with the annular flange portion 32 is a pair of axiallyextending, projecting, diametrically opposed lugs 33 which are receivedwithin the slots 18 provided in the flange portion 16 of driver D. Thecircumferential extent of the slots 18 is greater than thecircumferential extent of the lugs 33 to provide a lost motionconnection between the drive member D and the shaft S which permits alimited relative angular displacement of the drive member D relative tothe screw shaft S.

To prevent rotation of the screw shaft S when it is not being rotated bythe driver D, a flat disc, generally indicated at 35, is provided whichis rotatably mounted on the screw shaft portion 20. A pair of radiallyextending slots 36 are provided in communication with the bore 35a indisc 35 to also receive the axially extending lugs 33. As shown in thedrawing, the circumferential extent of the slots 36 is substantiallylarger than the circumferential extent of the lugs 33, thereby alsoproviding a lost motion connection therebetween, permitting the screwshaft S to be moved slightly relative to the disc 35 without effectingany movement thereof. The disc 35 is also provided with a plurality ofcircumferentially spaced apart notches 35b (FIG. about the outerperiphery thereof for a purpose to be presently described.

At the upper end of the housing H, as viewed in the drawing, a verticalbore 40 is provided in the annular boss 8a and receives a sleeve 41which is internally threaded at its upper end to receive an adjustablenut 42. A hollow plunger 43 is received within the sleeve 41 andincludes a locking detent 43a at its terminal end. A compression spring44 constantly acts on the plunger 43 to yieldably urge the detent 43atoward the disc 35. When the detent 43a engages in one of the recesses35b, the shaft S cannot be rotated because the lugs 33, after limitedrotational movement, engage the stationary sides of the slots 36, thushalting any further rotational movement. The detent 43a is movable, fromthe disc engaging position, shown in FIG. 6, to the radi-' ally outernon-engaging position shown in FIG. 7 to permit the driver D to drivethe shaft 20. When the driver D is driven, it drives the lockdisengaging flange 16 relatively to the disc 35 which causes the camsurfaces 16b to move the detent 43a to the removed position.

With the apparatus initially in the rest position illustrated in FIG. 6,the screw shaft S and disc 35 are prevented from rotating due toapplication of load L relative to the housing I-I because the detend 43aof the plunger 43 is in engagement with one of the notches 35b of thedisc 35. In this position of the parts, the slots 18 in the driver D aresubstantially aligned with the slots 36 in the disc 35 and the loadapplying member L exerts an axially directed force on the nut 24 in thedirection of the arrow a. This force will tend to rotate the screw shaftS in the direction of the arrow b until the sides 33a of the lugs 33 arein engagement with the sides 36a of the slots 36 after which timemovement is prevented.

When it is desired to positively move the load L toward the left asviewed in FIG. 1, the drive member D is rotated clockwisely in thedirection of the arrow 0 and the sides of the slots 18 engage the sides33a of the lugs 33 to move the lugs 33 from the full line position shownin FIG. 6 to the full line position shown in FIG. 7. During this initialrotation of the drive member D and shaft S, the detent 43a remainsengaged in one of the recesses 35b. With continued rotation of thedriver D, the cam surfaces 16b push the plunger 43 radially outwardly,overcoming the spring 44 with a gradual camming action, until the lobes16a are axially aligned with the slots 35b of the disc 35 and theplunger detent 43a is completely removed from the slot 35b in which itwas engaged. Although the disc 35 is fixed until the detent 43a isremoved, the lost motion connection between the slots 36 and the lugs 33permits rotation of the shaft S by the driver D.

When the load L has been properly positioned, and the rotative forceapplied to the driver D is removed, the force of the load L on therecirculating nut 24 tends to move the nut 24 in the direction of thearrow a, thus tending to cause the shaft 22 to rotate in the directionof the arrow b. The sides 33a of the lugs 33, engaging the sides 180 ofthe slots 18 will move the driver D slightly counterclockwisely oppositeto the direction of the arrow 0. Because of the lost motion connectionbetween the lugs 33 and the slots 36, the disc 35 remains stationarywhile the driver D is moving counterclockwisely to the position shown inFIG. 6 so that the detent 43a will again be received by a notch 35b onthe outer periphery of the disc 35 to lock the disc 35 in position. Thesides 33a of tabs 33 will engage the sides 36a of the slots 36 in disc35 to prevent any further reverse rotation and provide a positiveno-back lock. It can thus be seen that there is substantially no reverserotation of the shaft S possible.

Should the thrust force of the load L be suddenly reversed in adirection opposite to the arrow 0 when the drive apparatus is beingutilized to move the nut 24 and load L in toward the left as viewed inFIG. 1, the nut 24 will exert a force on the shaft S in a directionopposite the arrow b to drive the shaft S at a faster rate than thedriver D. The sides 33b of the lugs 33 will drive the side walls 36b ofthe slots 36 to move the disc 35 clockwisely relative to the driver D.The driver D is not affected by such a sudden overrunning movement ofthe shaft S because the lost motion connection between the shaft S anddriver D permits the lugs 33 to move freely within the slots 18 as thesides 33b of the lugs 33 approach the sides 18b. This relative movementwill enable the detent 43a to be moved radially inwardly along thecamming surface 16b to be received within a notch 35b of the driver 35,thereby quickly stopping any runaway action. Thus, it can be seen that apositive acting bidirectional no-back mechanism has been provided.

When it is desired to move the load L toward the right as viewed in FIG.1, the driver D is merely rotated counterclockwisely, opposite thedirection of rotation indicated by the arrow c, so that the slot sides18b of the driver flange 16, after a slight lost motion, will engage thesides 33b of the lugs 33 to drive the shaft S in the opposite direction.The lost motion connection between the lugs 33 and the disc 35 willpermit the shaft S to be rotated relative thereto while one of thesurfaces 16b cams the detent 43a radially outwardly in a manner similarto that previously described. The noback mechanism operatesbi-directionally in a similar manner when the drive is removed and toprevent overrunning. v

It should be realized that, although the driver flange l6 and disc 35are shown as provided with 8 corresponding notches and lobes, as thediameter of the apparatus is increased, more notches and lobes can beprovided.

It is to be understood that the drawings and descriptive matter are inall cases to be interpreted as merely illustrative of the principles ofthe invention, rather than limiting the same in any way, since it iscontemplated that various changes may be madein various elements toachieve like results without departing from the spirit of the inventionor the scope of the appended claims.

lclaim:

1. Apparatus comprising:

a support member;

a rotatable output member rotatably mounted by said support member; Q

a rotatable drive member for rotating said rotatable output member ineither direction;

means for releasably locking said output member to said support memberand releasably preventing the rotation of said output member when saidoutput member is not being driven by said drive member in eitherdirection including: detent means on one of said support and outputmembers, and detent receiving means, mounted on the other of saidsupport and output members for movement relative thereto, for removablyreceiving said detent means, and means for yieldably urging said detentmeans and said detent receiving means into engagement to lock saidoutput member to said support member and prevent the rotation of saidoutput member; whereby said output member has substantiallyinstantaneously prevented from rotating after limited relative rotarymovement of said output member and said locking means when said outputmember is not being driven by the input member in either direction; and

releasing means cooperating with said drive member 5 for relativelymoving said detent means and said detent receiving means to overcomesaid yieldable means to release said locking means and automaticallyunlock said output member from said support member when said drivemember is rotated in 10 either direction.

2. Apparatus as set forth in claim 1 wherein said detent means ismounted on said support member; and said braking means includes abraking plate movably mounted on said output member, said detentreceiving means comprising a plurality of recesses about the outerperiphery of said braking plate to releasably receive said detent means.

3. Apparatus as set forth in claim 2 wherein said releasing meanscomprises a plurality of perimetrically spaced cam means for moving saiddetent means out of one of said recesses when said drive member isrotated.

4. Apparatus as set forth in claim 2 wherein said braking plate iscoupled to said output member with a lost motion connection so as to bemovable therewith after limited relative angular displacement of theoutput member and braking plate.

5. Apparatus as set forth in claim 4 wherein said drive member iscoupled to said output member with a lost motion connection so as todrive said output member after limited relative angular displacementbetween the drive member and output member.

6. Apparatus as set forth in claim 1 wherein said releasing meanscomprises means on said drive member being displaceable relative to saidbrake means when said drive member is rotated to release said brakingmeans.

7. Apparatus as set forth in claim 6 wherein said drive member isconnected to said output member with a lost motion connection.

8. Apparatus comprising:

a rotatable output member;

a rotatable input member for driving the output member;

lock means including a part with a hub portion mounted on said outputmember with a rotary lost motion driving connection and a cooperatingportion movable from a locked position for preventing rotation of saidoutput member in cooperation with said part to a non-locking position,after relamember; and

means responsive to rotation of the input member in either direction formoving said lock means from locking position.

9. Apparatus as set forth in claim 8 wherein said rotatable input memberis connected to said output member with a lost motion connection topermit relative movement of said input member and said brake means.

10. In combination:

screw means cooperating with nut means for translating rotary motioninto linear motion when one of said screw means and nut means is rotatedto linearly move a load exerting a thrust force on the other of saidscrew means and nut means;

rotatable drive means connected to said one means with a rotary lostmotion driving connection for rotating said one means in eitherdirection;

lock means including a part with a hub portion mounted on said one meanswith a lost motion connection and having a cooperating portion movablebetween a locking position for preventing, in cooperation with saidpart, rotation of said one means and a non-locking position afterrelative angular displacement between said lock means and said one meansin a first direction, said cooperating portion being returnable to saidlocking position after relative rotary displacement of said one meansand lock means in an opposite direction; whereby said one means issubstantially instantaneously locked after limited relative rotation ofsaid one means and said locked means in said opposite direction; and

means responsive to rotation of the input member in either direction formoving said lock means from said locking position to said non-lockingposition, said one means and said lock means being relatively angularlydisplaced in a first direction in response to rotation of said drivemeans and relatively angularly displaced in said second direction inresponse to a rotation of said one means by said other means resultingfrom the thrust force exerted by said load on said other means.

11. The combination as set forth in claim 10 including a housing means;said lock means comprising:

recess means on said part,

detent means comprising said cooperating portion on said housing means,and

biasing means for constantly, yieldahly urging said detent means towardsaid recess means to a locking position to prevent rotation of said onemeans;

said detent means being movable to a non-locking position to permit saidone means to be freely driven by said drive means.

said means for moving said lock means including means on said drivemeans for moving said detent means against the force of said biasingmeans from said locking position to said non-locking position when saiddrive means drives said one means relative to said lock means in saidfirst direction and to permit said detent means to return from saidnonlocking position to said locking position when said lock means andsaid one means are relatively rotated in said opposite direction.

12. The combination as set forth in claim 11 wherein said lock meansincludes a braking plate mounted on said one means, said recess meanscomprises a plurality of radially outwardly facing recesses perimetrallyspaced about said braking plate, said detent means being radiallymovably mounted on said housing, said means for moving said detent meanscomprising a plurality of perimetrally spaced cam means on said drivemeans for moving the detent means out of one of said recesses when saiddrive means drives said one means.

13. The combination as set forth in claim 12 wherein said plurality ofcam means comprises an annular portion forming a plurality ofcircumferentially interposed raised and recessed portions, each of saidraised portions extending perimetrically, the width of one of saidrecesses.

14. The combination as set forth in claim 11 wherein said lost motionconnection between said one means and said brake means includes anaxially extending drive lug on said one means and cooperating drive lugreceiving means on said lock means, said drive lug and drive lugreceiving means being relatively circumferentially movable to permitrelative movement of said one means and said screw means when saiddetent means moves from said non-braking position to said brakingposition and said screw means is rotated in said opposite direction.

15. The combination as set forth in claim 11 wherein said one means issaid screw means including a screw shaft mounting a sleeve includingcircumferentially spaced, axially extending drive lugs; said lock meanscomprising a disc mounted on said shaft for limited rotation relativethereto and having apertures therein receiving said drive lugs to formsaid lost motion connection to permit limited relative rotation of saidsleeve and said disc, said recess means comprising a plurality ofcircumferentially spaced apart notches about the periphery of said discfor receiving said detent means.

16. The combination as set forth in claim 15 wherein said detent meanscomprises a radially movable plunger mounted on said housing, saidbiasing means biasing said plunger radially inwardly to be received byone of said notches; said means for moving said lock means including anundulating rim portion on said drive means engageable with said plungerto move said plunger radially outwardly when said drive means rotatessaid screw shaft, and said lost motion connection between said drivemeans and said screw shaft comprises apertures in said drive meansreceiving said drive lugs and permitting movement of said drive lugsrelative to said recesses in said drive means.

17. Apparatus comprising:

a rotatable output member;

a rotatable input member connected to said output member with a lostmotion connection for driving said output member in either direction;

lock means including a part with a hub portion rotatably mounted on saidoutput member with a lost motion connection and having a cooperatingportion movable from a locking position for preventing, in cooperationwith said part, rotation of said output member to a non-lockingposition, in response to relative angular displacement of said lockmeans and said input member in a first direction, said second portionbeing returnable to said locking position in response to relativeangular displacement of said lock means and said input member in anopposite direction; whereby said output member is substantiallyinstantaneously locked after limited rotary movement of said outputmember and said lock means in said opposite direction;

said input member and said lock means being relatively angularlydisplaced in said first direction in response to rotation of said outputmember by said input member.

1. Apparatus comprising: a support member; a rotatable output memberrotatably mounted by said support member; a rotatable drive member forrotating said rotatable output member in either direction; means forreleasably locking said output member to said support member andreleasably preventing the rotation of said output member when saidoutput member is not being driven by said drive member in eitherdirection including: detent means on one of said support and outputmembers, and detent receiving means, mounted on the other of saidsupport and output members for movement relative thereto, for removablyreceiving said detent means, and means for yieldably urging said detentmeans and said detent receiving means into engagement to lock saidoutput member to said support member and prevent the rotation of saidoutput member; whereby said output member has substantiallyinstantaneously prevented from rotating after limited relative rotarymovement of said output member and said locking means when said outputmember is not being driven by the input member in either direction; andreleasing means cooperating with said drive member for relatively movingsaid detent means and said detent receiving means to overcome saidyieldable means to release said locking means and automatically unlocksaid output member from said support member when said drive member isrotated in either direction.
 2. Apparatus as set forth in claim 1wherein said detent means is mounted on said support member; and saidbraking means includes a braking plate movably mounted on said outputmember, said detent receiving means comprising a plurality of recessesabout the outer periphery of said braking plate to releasably receivesaid detent means.
 3. Apparatus as set forth in claim 2 wherein saidreleasing means comprises a plurality of perimetrically spaced cam meansfor moving said detent means out of one of said recesses when said drivemember is rotated.
 4. Apparatus as set forth in claim 2 wherein saidbraking plate is coupled to said output member with a lost motionconnection so as to be movable therewith after limited relative angulardisplacement of the output member and braking plate.
 5. Apparatus as setforth in claim 4 wherein said drive member is coupled to said outputmember with a lost motion connection so as to drive said output memberafter limited relative angular displacement between the drive member andoutput member.
 6. Apparatus as set forth in claim 1 wherein saidreleasing means comprises means on said drive member being displaceablerelative to said brake means when said drive member is rotated torelease said braking means.
 7. Apparatus as set forth in claim 6 whereinsaid drive member is connected to said output member with a lost motionconnection.
 8. Apparatus comprising: a rotatable output member; arotatable input member for driving the output member; lock meansincluding a part with a hub portion mounted on said output member with arotary lost motion driving connection and a cooperating portion movablefrom a locked position for preventing rotation of said output member incooperation with said part to a non-locking Position, after relativeangular displacement of said brake means and said output member in afirst direction, said cooperating portion being returnable to saidlocking position after relative angular displacement of said lock meansand said output member in an opposite direction; whereby said outputmember is substantially instantaneously locked after limited rotarymovement of said output member and said lock means in said oppositedirection; said output member and said part being relatively angularlydisplaced in said first direction in response to rotation of said outputmember by said input member; and means responsive to rotation of theinput member in either direction for moving said lock means from lockingposition.
 9. Apparatus as set forth in claim 8 wherein said rotatableinput member is connected to said output member with a lost motionconnection to permit relative movement of said input member and saidbrake means.
 10. In combination: screw means cooperating with nut meansfor translating rotary motion into linear motion when one of said screwmeans and nut means is rotated to linearly move a load exerting a thrustforce on the other of said screw means and nut means; rotatable drivemeans connected to said one means with a rotary lost motion drivingconnection for rotating said one means in either direction; lock meansincluding a part with a hub portion mounted on said one means with alost motion connection and having a cooperating portion movable betweena locking position for preventing, in cooperation with said part,rotation of said one means and a non-locking position after relativeangular displacement between said lock means and said one means in afirst direction, said cooperating portion being returnable to saidlocking position after relative rotary displacement of said one meansand lock means in an opposite direction; whereby said one means issubstantially instantaneously locked after limited relative rotation ofsaid one means and said locked means in said opposite direction; andmeans responsive to rotation of the input member in either direction formoving said lock means from said locking position to said non-lockingposition, said one means and said lock means being relatively angularlydisplaced in a first direction in response to rotation of said drivemeans and relatively angularly displaced in said second direction inresponse to a rotation of said one means by said other means resultingfrom the thrust force exerted by said load on said other means.
 11. Thecombination as set forth in claim 10 including a housing means; saidlock means comprising: recess means on said part, detent meanscomprising said cooperating portion on said housing means, and biasingmeans for constantly, yieldably urging said detent means toward saidrecess means to a locking position to prevent rotation of said onemeans; said detent means being movable to a non-locking position topermit said one means to be freely driven by said drive means. saidmeans for moving said lock means including means on said drive means formoving said detent means against the force of said biasing means fromsaid locking position to said non-locking position when said drive meansdrives said one means relative to said lock means in said firstdirection and to permit said detent means to return from saidnon-locking position to said locking position when said lock means andsaid one means are relatively rotated in said opposite direction. 12.The combination as set forth in claim 11 wherein said lock meansincludes a braking plate mounted on said one means, said recess meanscomprises a plurality of radially outwardly facing recesses perimetrallyspaced about said braking plate, said detent means being radiallymovably mounted on said housing, said means for moving said detent meanscomprising a plurality of perimetrally spaced cam means on said drivemeans for moving the detent means out of one of said recesSes when saiddrive means drives said one means.
 13. The combination as set forth inclaim 12 wherein said plurality of cam means comprises an annularportion forming a plurality of circumferentially interposed raised andrecessed portions, each of said raised portions extendingperimetrically, the width of one of said recesses.
 14. The combinationas set forth in claim 11 wherein said lost motion connection betweensaid one means and said brake means includes an axially extending drivelug on said one means and cooperating drive lug receiving means on saidlock means, said drive lug and drive lug receiving means beingrelatively circumferentially movable to permit relative movement of saidone means and said screw means when said detent means moves from saidnon-braking position to said braking position and said screw means isrotated in said opposite direction.
 15. The combination as set forth inclaim 11 wherein said one means is said screw means including a screwshaft mounting a sleeve including circumferentially spaced, axiallyextending drive lugs; said lock means comprising a disc mounted on saidshaft for limited rotation relative thereto and having apertures thereinreceiving said drive lugs to form said lost motion connection to permitlimited relative rotation of said sleeve and said disc, said recessmeans comprising a plurality of circumferentially spaced apart notchesabout the periphery of said disc for receiving said detent means. 16.The combination as set forth in claim 15 wherein said detent meanscomprises a radially movable plunger mounted on said housing, saidbiasing means biasing said plunger radially inwardly to be received byone of said notches; said means for moving said lock means including anundulating rim portion on said drive means engageable with said plungerto move said plunger radially outwardly when said drive means rotatessaid screw shaft, and said lost motion connection between said drivemeans and said screw shaft comprises apertures in said drive meansreceiving said drive lugs and permitting movement of said drive lugsrelative to said recesses in said drive means.
 17. Apparatus comprising:a rotatable output member; a rotatable input member connected to saidoutput member with a lost motion connection for driving said outputmember in either direction; lock means including a part with a hubportion rotatably mounted on said output member with a lost motionconnection and having a cooperating portion movable from a lockingposition for preventing, in cooperation with said part, rotation of saidoutput member to a non-locking position, in response to relative angulardisplacement of said lock means and said input member in a firstdirection, said second portion being returnable to said locking positionin response to relative angular displacement of said lock means and saidinput member in an opposite direction; whereby said output member issubstantially instantaneously locked after limited rotary movement ofsaid output member and said lock means in said opposite direction; saidinput member and said lock means being relatively angularly displaced insaid first direction in response to rotation of said output member bysaid input member.